It was the 10th straight day that Chinese vessels have been spotted around the islet chain in the East China Sea.

The coast guard said one of its vessels warned the Chinese ships not to enter Japan’s territorial waters but received no response. The ships left the so-called contiguous zone, adjacent to the territorial waters, after 6 a.m. but re-entered around 7 a.m., the 11th Regional Coast Guard Headquarters in Naha, Okinawa Prefecture, said.